When tires become worn, they may be restored with new tread bands or tread layers during a retread process. Retreading is a restoration or re-manufacturing process that not only extends the service life of the tires, but also is significantly less expensive than manufacturing new tires. FIG. 1 shows an exemplary tire 10 that may be subject to retreading. Tire 10 has a tire casing 12 with a crown section 14, shoulders 16, reinforcement 18 and sidewall 20. Crown section 14 may have been buffed or otherwise worked to provide a prepared bonding surface to which a laterally extending tread 22 can be bonded (e.g., via one or more bonding layers). One or more tread elements (not shown) may be integral with tread 22 in a variety of configurations as known in the art. It is therefore understood that the configuration of tread 22 is not limited to that shown herein and that a variety of tread configurations are amenable for use with the carcass.
The manufacture of various treads is effected according to multiple processes that employ a variety of molds and presses. In some production facilities, dual molds are utilized that have two single flat molds and use a permanent center dividing ridge (or “rib”). This dual mold is cast as a single piece and is not repairable. An exemplary dual mold as known in the art is provided FIG. 2, wherein one or more dual mold segments 50 are employed to form an exemplary tread having a length extending linearly or annularly. One or more of dual mold segments 50 may be selectively arranged to form a molded tread having an outer, tire-operating side (also referred to herein as the “ground-engaging side” of the tread). The tire-operating side of the tread includes exposed surfaces that are configured to engage a ground surface upon which the tire operates (i.e., the ground-engaging side of the tread extends annularly about the tire).
It is understood that the molded tread may exhibit any one of a plurality of configurations without departing from the scope of the present disclosure. As such, each dual mold segment 50 may have a plurality of integral tread-molding elements 55 formed in each of tread molding cavities 57, 59. Tread molding elements 55 enable the selective formation of one or more tread performance features, including but not limited to one or more of sipes, ribs, patterns of ribs, grooves, traction edges, slotted shoulders, tread blocks and other features selected to impart desired performance characteristics to a tire formed with the molded tread. Each tread molding cavity 57, 59 may also be configured to receive, shape and form other portions of the tire, such as opposing tire side walls and portions thereof. Each dual mold segment 50 exhibits an exemplary tread pattern, and a person of ordinary skill in the art will appreciate that the tread pattern is not limited by the present disclosure.
Referring further to FIG. 2, each dual mold segment 50 incorporates an integral center rib 60 separating tread cavities 57, 59. As schematically depicted by FIG. 3, a center rib 60 such as that shown in FIG. 2 typically has a contact surface 60a having a top width W and a height HΔ that is below the mold edge height HM. In such dual molds, the center rib is the weakest point of the entire mold and gets damaged even with the normal operation of the mold. During tread production, at least one platen (not shown) contacts the center rib (e.g., contact surface 60a) upon press closure, as is known in the art. The center rib is susceptible to crushing by such platen, especially when subject to repeated contact thereby (an example of such a crushed center rib is shown by rib 60′ in FIG. 2). Over an extended number of cures, even following best production practices, press closure can damage a current dual mold segment beyond repair (in some cases, resulting in the loss of a costly mold and the loss of dual mold capacity for up to four months). In such circumstances, the entire mold must be replaced, thereby incurring significant temporal lapses in production and consequent financial losses.
A mold configuration is therefore demanded that accommodates in-house repair of damaged ribs and thereby reduces downtime for mold replacement.